Water on extended and point defects at MgO surfaces

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Understanding water-surface interactions is crucial for catalysis and materials degradation.
• Magnesium oxide (MgO) surfaces, particularly those with defects, exhibit unique chemical properties.
• Previous studies focused on flat MgO surfaces, leaving step defect interactions less explored.

Purpose of the Study:

• To investigate water adsorption and dissociation on MgO(100) surface steps.
• To determine the influence of step morphology and coordination on water interaction.
• To elucidate the role of electrostatic interactions in stabilizing adsorbed species.

Main Methods:

• First-principles simulations (density functional theory).
• Analysis of water adsorption energies and configurations.
• Investigation of hydroxyl group coordination and proton diffusion.

Main Results:

• Water adsorption is dissociative on MgO(100) mono- and diatomic steps, unlike flat terraces.
• Hydroxyl groups exhibit varied coordination (2-, 4-, and 1-fold) depending on step structure.
• Electrostatic interactions between hydroxyls and protons significantly stabilize adsorbed species, hindering diffusion.

Conclusions:

• Water adsorption on MgO steps is primarily governed by the coordination of the surface acid-base pair.
• Step defect structure critically influences hydroxyl group stability and proton mobility.
• Understanding these interactions is key to predicting water desorption behavior and surface reactivity.